I've looked at the Lease vs Buy for a MX 90D and here's where my numbers sit. Feel free to poke any holes in my calculations / assumptions:
Lease Option (Numbers from Tesla Design Studio)
36 months - 15K Miles - $1,472 = $52,992 + $7,167 at signing = $60,159 + Texas taxes on FULL MSRP of $6,900 (6.25%) = $67k
Buy Option
72 months - 2.15% - $5k deposit + $6,900 taxes = $11,900 down.
MSRP $110,400. Financing $105,400. P&I = $1,562 for 36 months = $56,232 + $11,900 down = $68,132 - Fed Tax Rebate $7,500 = $60,632.
I will probably drive about 54k miles in 3 years which would put me 9k miles over the lease or $2,250 extra.
After 3 years I would have paid $69,250 LEASE or $60,632 BUY.
I would owe $54,292 on loan which is 49.2% of MSRP of $110,400.
To me the BUY option is a LOT better. The Residual value after 36 months would have to be 41.4% for me to still break even between the 2 options. It's also a lot easier to keep the car for year 4 if you still want it then but also have paid off enough of the loan to not be worried about being upside down.
Gas savings are NOT included since it's the same for either option.
Here's the sheet that I'm using. Feel feel to plug in your own numbers and suggest modifications.
Tesla Model X Finance